Electric working machine

ABSTRACT

An electric working machine capable of efficiently cooling components disposed inside, as well as simplifying assembling work and reducing man-hours and production cost. A motor, control board for controlling the motor, rod fixture secured to the front side of the motor, and air guiding partitioning member secured to the rear side of the motor form a motor assembly. The air guiding partitioning member includes a partitioning plate hermetically partitioning between air exhaust and intake ports provided with a predetermined interval longitudinally in the body casing. The partitioning plate has an air guiding window for delivering cooling air taken in from the air intake port to an opening for sucking air on the front side of the motor through a space between the motor and body casing. The control board is disposed on the rear side of the partitioning plate.

RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2020-010307, filed on Jan. 24, 2020, the entire content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to an electric working machine driven byan electric motor to be operated, such as a bush cutter, hedge trimmer,and chain saw.

2. Description of the Related Art

Portable electric working machines driven by an electric motor(hereinafter simply referred to as a motor) to be operated typicallyinclude a motor as the driving source for operation, a control board forcontrolling the motor or the like, battery, and the like disposed insidea body casing. The temperature inside the body casing (generated heatamount of components disposed inside thereof) is comparatively lowerthan that of working machines driven by an engine, but is still likelyto become high in some cases. When the temperature inside the bodycasing becomes high, the components disposed inside are likely todeteriorate. Therefore, as disclosed in US 2010/0218385 A1 or the like,approaches have conventionally been taken, such as, with a cooling fanprovided in the motor, sucking the outer air into the body casing toavoid heat stagnant inside and blowing cooling air onto the componentssupposed to have a high temperature.

SUMMARY OF THE INVENTION

However, in the conventional electric working machines, ahigh-temperature air to be exhausted from the body casing mixes with alow-temperature cooling air taken into the body casing. Thus, theircooling performance has not been efficient.

Further, the components such as the motor are individually attached tothe body casing, which has raised another problem of requiring labor andtime for assembling work.

In view of the foregoing, the present disclosure provides an electricworking machine capable of efficiently cooling the components disposedinside, as well as simplifying the assembling work and reducing theman-hours and production cost.

Considering the foregoing, the electric working machine according to thepresent disclosure basically includes a motor as the driving source foroperation, a body casing in which the motor is disposed in thelongitudinal direction, an operating rod provided with a working part,and a rod fixture for securely attaching the operating rod to the bodycasing.

Further, the motor, the control board for controlling the motor, the rodfixture secured to the front side of the motor, and an air guidingpartitioning member secured to the rear side of the motor form a motorassembly. The air guiding partitioning member includes a partitioningplate that hermetically partitions between an air exhaust port and anair intake port provided with a predetermined interval in thelongitudinal direction in the body casing, the partitioning plateprovided with an air guiding window for delivering cooling air taken infrom the air intake port to an opening for sucking air on the front sideof the motor through a space between the motor and the body casing. Thecontrol board is disposed on the rear side of the partitioning plate.

In some embodiments, the air exhaust port and the air intake port areprovided on a bottom of the body casing in the longitudinal direction,and the air guiding window is provided in the upper portion of thepartitioning plate.

In some embodiments, the electronic components that are supposed to havea high temperature are mounted in a lower portion of the control board,and a guide member with a widened and open lower portion is provided inthe control board to allow more cooling air taken in from the air intakeport to flow through the electronic components that are supposed to havea high temperature.

In another embodiment, the guide member is integrally formed with thepartitioning plate.

In yet another embodiment, the air guiding partitioning member includesa recessed housing that covers at least part of a fan case provided in arear portion of the motor.

In still another embodiment, the body casing has a single cylindricalbody with an open front end and an open rear end and with a partitioningwall portion that partitions the inside of the body casing into a frontportion and a rear portion. The rod fixture includes a mounting basedisposed behind the partitioning wall portion and is securely fastenedto the partitioning wall portion, with at least one bolt screwed fromthe front side to the rear side of the partitioning wall portion througha through-hole provided in the partitioning wall portion, and a tubularfixture for securing the proximal end of the operating rod, the tubularfixture projecting from the mounting base toward the front of thepartitioning wall portion through an insertion hole provided in thepartitioning wall portion.

In the electric working machine according to the present disclosure, themotor, control board, rod fixture, and air guiding partitioning memberare integrally formed as a motor assembly as a single article. This cansimplify and accelerate the assembling work.

In addition, with the air guiding partitioning member partitioning theair exhaust port and the air intake port, a high-temperature exhaust airis unlikely to mix with a low-temperature intake air. Further, thecontrol board is disposed on the rear side of the partitioning plate toallow the cooling air from the air intake port to be easily blown ontothe electronic components that are supposed to have a high temperature.Thus, the control board can be efficiently cooled and the electroniccomponents (such as the capacitor) mounted on the control board are lesslikely to deteriorate due to the heat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a common machine body and three types ofexchangeable working parts of an embodiment of an electric workingmachine according to the present disclosure;

FIG. 2 is a perspective view showing the inside of the electric workingmachine illustrated in FIG. 1 with a cap removed from the front end of abody casing;

FIG. 3 is a perspective view showing the inside of the electric workingmachine illustrated in FIG. 1 as viewed from a cut-out portion near theproximal end of an operating rod and a cut-out front portion of the bodycasing;

FIG. 4 is a longitudinal cross-sectional view of the proximal end of theoperating rod and the front half portion of a body of the electricworking machine illustrated in FIG. 1;

FIG. 5 is a perspective view of a motor assembly illustrated in FIG. 4as diagonally viewed from the front side;

FIG. 6 is a perspective view of the motor assembly illustrated in FIG. 4as diagonally viewed from the rear side;

FIG. 7 is an exploded perspective view of a rod fixture, a motor, and anair guiding partitioning member that form the motor assembly illustratedin FIG. 4 as diagonally viewed from the front side;

FIG. 8 is an exploded perspective view of the rod fixture, the motor, acontrol board, and the air guiding partitioning member that form themotor assembly illustrated in FIG. 4 as diagonally viewed from the rearside;

FIG. 9 is a view for explaining an assembling process (first process) ofthe body of the electric working machine illustrated in FIG. 1;

FIG. 10 is a perspective view of the body illustrated in FIG. 9 uponcompletion of the assembling process (first process);

FIG. 11 is a view for explaining an assembling process (second process)of the body of the electric working machine illustrated in FIG. 1;

FIG. 12 is a view for explaining an assembling process (third process)of the body of the electric working machine illustrated in FIG. 1;

FIG. 13 shows schematic views for explaining the configuration of atemporarily securing mechanism illustrated in FIG. 9;

FIG. 14 shows perspective views for explaining the functional effects ofthe temporarily securing mechanism illustrated in FIG. 9;

FIG. 15 is a schematic side view showing another example (example 1) ofthe temporarily securing mechanism illustrated in FIG. 9;

FIG. 16 is a schematic side view showing another example (example 2) ofthe temporarily securing mechanism illustrated in FIG. 9;

FIG. 17 is a schematic side view showing another example (example 3) ofthe temporarily securing mechanism illustrated in FIG. 9;

FIG. 18 is a schematic side view showing another example (example 4) ofthe temporarily securing mechanism illustrated in FIG. 9; and

FIG. 19 is an overall longitudinal cross-sectional view for explainingan air flow in the body of the electric working machine illustrated inFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exemplary embodiment of the present disclosure will be describedbelow with reference to the drawings.

[Configuration of Electric Working Machine]

FIG. 1 is a perspective view of a common machine body 10 and three typesof exchangeable working parts (also referred to as attachments) 50 (51,52, and 53) of an electric working machine 1 of an embodiment accordingto the present disclosure. FIG. 2 is a perspective view showing theinside of the electric working machine 1 illustrated in FIG. 1 with acap 13 removed from the front end of a body casing 23. FIG. 3 is aperspective view showing the inside of the electric working machine 1illustrated 1 in FIG. 1 as viewed from a cut-out portion near a proximalend 11 a of an operating rod 11 and a cut-out front portion of the bodycasing 23. FIG. 4 is a longitudinal cross-sectional view of the proximalend 11 a of the operating rod 11 and the front half portion of a body 20of the electric working machine 1 illustrated in FIG. 1.

The electric working machine 1 in the illustrated embodiment includesthe common machine body 10 with a motor 30 as the driving source foroperation and working parts 50 (51, 52, and 53) removably attached tothe common machine body 10. The common machine body 10 includes the body20 and the operating rod 11 (specifically, a main operating rod 11A thatforms the root portion or rear half portion of the operating rod 11).The body 20 has the synthetic resin body casing 23. The body casing 23has a single cylindrical body widened from the front end side toward therear end side (rearward) with open front and rear ends. The motor 30 isdisposed inside the body casing 23 in the longitudinal direction. Theoperating rod 11 is a straight pipe and the proximal end thereof issecurely attached to the front end of the body 20. A cap 13 covering thefront end of the body casing 23, a grip 14, a handle lever 15, and thelike are integrally and externally disposed around the proximal end ofthe operating rod 11, and a fan-shaped loop handle 17 is attached ontheir front side.

A power transmission shaft 12 supported by a bearing 58 (FIG. 4) extendsthrough the center of the operating rod 11. The transmission shaft 12 isadapted to transmit the rotary driving force of the motor 30 to theworking part 50 provided at the distal end of the operating rod 11.

The working part 50 includes several types of exchangeable working parts(attachments) 51, 52, and 53 (only three types of those shown herein).In the illustrated example, the working part 51, working part 52, andworking part 53 function as a bush cutter, hedge trimmer, and chain saw,respectively. The working parts 51, 52, and 53 each have the operatingrod 11 (specifically, a removable operating rod 11B that forms thedistal end portion or front half portion of the operating rod 11) andthe power transmission shaft 12, and are optionally removable by meansof a coupling fixture 18 and a power transmission connector (not shown)that are provided at the distal end of the main operating rod 11A.

A partitioning wall portion 24 is provided inside and near the front endof the cylindrical body casing 23. The partitioning wall portion 24partitions the inside of the body casing 23 into front and rearportions. A motor assembly 25 as shown in FIG. 5 to FIG. 8 is securelyattached to the partitioning wall portion 24. The motor assembly 25includes four components integrally formed, which are the motor 30, acontrol board 80 for controlling the motor 30 or the like, a rod fixture(also referred to as a fixture) 40 for securely attaching the proximalend 11 a of the operating rod 11 to the body casing 23, and an airguiding partitioning member 60.

The motor 30 includes a short cylindrical body 31. A base 32 with abearing is secured to the front side of the short cylindrical body 31. Arotary drive shaft 33 projects toward the front from the base 32. A fancase 34 is provided on the rear side of the short cylindrical body 31 soas to cover a cooling fan (vane) provided in the rear portion of therotary drive shaft 33. Herein, the short cylindrical body 31 and the fancase 34 are attached together by locking gate-like engagement pieces 37provided in the front end of the fan case 34, with hooks 38 provided(directed to the rear) at four locations in the rear end of the shortcylindrical body 31. A lower portion of the fan case 34 forms an airoutlet 34 a directed toward an air exhaust port 21 provided in the bodycasing 23. The portion excluding the base 32 on the front side of theshort cylindrical body 31 in the motor 30 forms an opening 36 for thecooling fan for sucking air.

The rod fixture 40 (a mounting base 42 thereof) is securely fastened,with three bolts 41, to the base 32 (that is, front side) of the motor30. The rod fixture 40 includes a rectangular thick plate-like mountingbase 42 and a tubular fixture 44. The mounting base 42 is disposedbehind the partitioning wall portion 24 of the body casing 23 so as tobe pressed against the partitioning wall portion 24 of the body casing23 from the rear side and is securely fastened to the partitioning wallportion 24, with four bolts 28 screwed from the front side to the rearside of the partitioning wall portion 24 through through-holes 27provided at four locations of the partitioning wall portion 24. Thetubular fixture 44 for securely fastening the proximal end 11 a of theoperating rod 11 projects from the center of the mounting base 42 towardthe front of the partitioning wall portion 24 through a key-shapedinsertion hole 26 provided in the partitioning wall portion 24. Thetubular fixture 44 is configured with an anchor bolt-type fastener 46having a slit cut-out portion 46 a on its upper side. Screw holes 45into which the four bolts 28 are screwed are provided at four corners ofthe mounting base 42.

The power transmission shaft 12 disposed inside the operating rod 11 issecurely coupled, at its proximal end 12 a, to the rotary drive shaft 33of the motor 30 disposed inside the tubular fixture 44 via a coupling 57(see FIG. 4).

The present embodiment additionally includes a configuration asdescribed below, so that in assembling the electric working machine 1(common machine body 10 thereof), the tubular fixture 44 and theinsertion hole 26 of the partitioning wall portion 24 (operating rod 11)are coaxially arranged and the through-holes 27 of the partitioning wallportion 24 for inserting the four bolts 28 and the screw holes 45 of themounting base 42 into which the bolts 28 are screwed are coaxiallyarranged.

Specifically, a temporarily securing mechanism 39 is provided forretaining the position of the motor assembly 25 by automatically movingthe motor assembly 25 in the rotating direction and two orthogonaldirections on a plane along (parallel to) the partitioning wall portion24 relative to the body casing 23, when the mounting base 42 is disposedbehind the partitioning wall portion 24 so as to allow the tubularfixture 44 to project toward the front of the partitioning wall portion24 through the insertion hole 26 of the partitioning wall portion 24 andsimultaneously, the mounting base 42 is pressed against the partitioningwall portion 24 from the rear side, prior to finally securing themounting base 42 of the rod fixture 40, with the four bolts 28, to thepartitioning wall portion 24 in the motor assembly 25.

The temporarily securing mechanism 39 specifically includes a pluralityof fitting pieces 49 and 49 (herein a left and right pair of fittingpieces) and a left and right pair of bracing pieces 29 and 29. Thefitting pieces 49 and 49 are spaced from each other with a predeterminedangle (herein, 180 degrees) in a thick portion (flange portion) 47 (rearface thereof) formed in the front end of the tubular fixture 44 (thatis, a portion of the tubular fixture 44 projecting toward the front ofthe partitioning wall portion 24). The bracing pieces 29 and 29corresponding to the left and right pair of fitting pieces 49 and 49 areprovided on the periphery of the insertion hole 26 of the partitioningwall portion 24.

The rear faces of the left and right pair of fitting pieces 49 and 49form fitting recesses 49 a and 49 a in an elliptic arc or a mountainshape as viewed from the side that are recessed forward.

The distal ends (faces) of the left and right pair of bracing pieces 29and 29 form fitting projections 29 a and 29 a in an elliptic arc or amountain shape as viewed from the side that can fit into the fittingrecesses 49 a and 49 a of the fitting pieces 49 and 49. Herein, as shownin the drawing on the left side of FIG. 13, the left and right pair ofbracing pieces 29 and 29 project diagonally forward (inclined inward) ina mirror symmetric manner from the periphery of the insertion hole 26 ofthe partitioning wall portion 24 with their distal ends closer to eachother. In the normal state (before temporarily secured), when theseparation between the distal ends of the left and right pair of bracingpieces 29 and 29 is represented by La, the diameter of the tubularfixture 44 (body thereof) is represented by Lb, and the diameter of thethick portion (flange portion) 47 is represented by Lc, La<Lb<Lc (FIG.13) or Lb<La<Lc is satisfied. Therefore, when the mounting base 42 isdisposed behind the partitioning wall portion 24 so as to allow thetubular fixture 44 to project toward the front of the partitioning wallportion 24 through the insertion hole 26 of the partitioning wallportion 24 and simultaneously, the mounting base 42 is pressed againstthe partitioning wall portion 24 from the rear side, the bracing pieces29 and 29 are elastically widened by the tubular fixture 44 and theirdistal ends are elastically pressed against the side surface of thetubular fixture 44, as shown in the drawing on the right side of FIG.13. Eventually, the fitting projections 29 a and 29 a at the distal endsfit into the fitting recesses 49 a and 49 a of the fitting pieces 49 and49 (which will be detailed later).

The shapes of the rear face of the fitting piece 49 and the distal endface of the bracing piece 29 may be inverted from those described above.That is, the rear face of the fitting piece 49 may form a fittingprojection 49 b in an elliptic arc as viewed from the side, while thedistal end face of the bracing piece 29 may form a fitting recess 29 bin an elliptic arc as viewed from the side that is recessed rearward(FIG. 15). Alternatively, the rear face of the fitting piece 49 may forma fitting projection 49 c in a mountain shape as viewed from the side,while the distal end face of the bracing piece 29 may form a fittingrecess 29 c in a mountain shape as viewed from the side that is recessedrearward (FIG. 16).

In the present example, the fitting pieces 49 and 49 are provided in thethick portion (flange portion) 47 (rear face thereof) of the tubularfixture 44, but may be provided in a portion other than the thickportion (flange portion) 47 of the tubular fixture 44. For example, theside surface of the tubular fixture 44 may be provided with the fittingpiece 49 having, on its rear face, a fitting recess 49 d in an ellipticarc or a mountain shape as viewed from the side that is recessed forwardin the same shape as that of the present example (FIG. 17).Alternatively, the side surface of the tubular fixture 44 may beprovided with the fitting piece 49 as a projection in a circular shapeas viewed from the side (FIG. 18). In the example shown in FIG. 18, therear face of the fitting piece 49 forms a fitting projection 49 e in anelliptic arc as viewed from the side, while the distal end face of thebracing piece 29 forms a fitting recess 29 e in an elliptic arc asviewed from the side that is recessed rearward.

The air guiding partitioning member 60 that forms the rear portion ofthe motor assembly 25 is made of, for example, a synthetic resin. Theair guiding partitioning member 60 includes a recessed housing 63 and apartitioning plate 62. The recessed housing 63 covers at least an upperhalf portion of the fan case 34 (a portion on the front side of asubstantially fan-shaped air guiding window 64, which will be describedlater) provided in the rear portion of the motor 30. The partitioningplate 62 substantially hermetically partitions between the air exhaustport 21 and an air intake port 22 provided with a predetermined intervalin the longitudinal direction on a bottom 23 b (in a portion behind thepartitioning wall portion 24) of the body casing 23. The upper portion(on the upper side of the recessed housing 63) of the partitioning plate62 is provided with the air guiding window 64 for delivering cooling airtaken in from the air intake port 22 to the opening 36 for sucking airon the front side through a space 66 between the motor 30 and the bodycasing 23 (see, in particular, FIG. 4 and FIG. 19). Herein, the airguiding partitioning member 60 is securely attached to the rear side ofthe motor 30 by screwing one bolt 69 from the rear side of thepartitioning plate 62 into the fan case 34, but may be attached to therear side of the motor 30 through snap-fit or the like instead of or incombination with the securement with the bolt 69. The outer surface inthe front end of the recessed housing 63 is provided with three recesses68 for avoiding interference with the hooks 38 (portions projectingtoward the rear from the gate-like engagement piece 37 of the fan case34) of the short cylindrical body 31.

The shape of the partitioning plate 62 is substantially the same as thatof the body casing 23 (inner periphery shape thereof). The outerperiphery surface of the partitioning plate 62 faces in contact with theinner periphery surface of the body casing 23. The body casing 23 isreinforced by the partitioning plate 62 so as not to be easily dent. Therear side of the partitioning plate 62 is provided with a housing 88 fora ferrite electromagnetic wave absorber.

The rear side of the partitioning plate 62 disposed between the airexhaust port 21 and the air intake port 22 is provided with the controlboard 80 in the vertical direction. The control board 80 has mountedthereon a microcomputer including an FET, ROM, RAM, input/outputcircuit, and the like, and other necessary electronic components such asa capacitor 82 and a connector 84. In this case, the components supposedto have a high temperature in the control board 80, such as the FET andcapacitor 82, are positioned in a lower portion closer to the air intakeport 22. The FET is covered with a cooling fin 85.

The partitioning plate 62 of the air guiding partitioning member 60 isintegrally formed with a guide member 67 with open upper and lowerportions to cover the surroundings (side and rear surfaces) of the FET(cooling fin 85) and the capacitor 82, which are supposed to have a hightemperature. The lower portion of the guide member 67 opens wider (thanthe upper portion) to allow more cooling air taken in from the airintake port 22 to flow through the FET (cooling fin 85) and thecapacitor 82, which are supposed to have a high temperature.

The rear portion (that is, rear side of the motor assembly 25) of thebody casing 23 has a battery case 92 for housing (slot housing) abattery 90, securely attached with a predetermined number of bolts 93(see FIG. 1 and FIG. 11).

[Method for Assembling Electric Working Machine]

Next, an exemplary method for assembling the electric working machine 1(body 20 thereof) configured as described above, particularly, anexemplary process for attaching the motor assembly 25 to the body casing23 will be described.

First, as illustrated in FIG. 9, the body casing 23 is placed verticallywith its front side positioned lower and the motor assembly 25 is placedwith the rod fixture 40 side positioned lower. Then, the motor assembly25 is relatively inserted into the body casing 23 such that the shape ofthe motor assembly 25 (partitioning plate 62 of the air guidingpartitioning member 60 thereof) fits the inner shape of the body casing23, and the mounting base 42 is pressed against the partitioning wallportion 24. This causes the tubular fixture 44 to elastically press towiden the bracing pieces 29 and 29 with their distal ends to beelastically pressed against the side surface of the tubular fixture 44,and the fitting projections 29 a and 29 a at the distal ends of thebracing pieces 29 and 29 fit into the fitting recesses 49 a and 49 a ofthe fitting pieces 49 and 49, as illustrated in the drawing on the rightside of FIG. 13. In this manner, the motor assembly 25 is temporarilysecured (temporarily attached) to the body casing 23 (see FIG. 10).

In this case, as illustrated in the drawing on the left side of FIG. 14,the fitting projections 29 a and 29 a may not exactly fit into thefitting recesses 49 a and 49 a. After conducting connecting and wiringin the control board 80, with the motor assembly 25 inserted into thebody casing 23 as described above, the battery case 92 is securelyfastened with a predetermined number of bolts 93 to the body casing 23as illustrated in FIG. 11, and then, when the body casing 23 (body 20)is inverted as illustrated in FIG. 12, the fitting recesses 49 a and 49a and fitting projections 29 a and 29 a of the temporarily securingmechanism 39 tightly fit together with their sliding alignment function,as illustrated in the drawing on the right side of FIG. 14. Due to suchfitting, the motor assembly 25 automatically moves in the rotatingdirection and two orthogonal directions on a plane along (parallel to)the partitioning wall portion 24. In this manner, an axis Jb of thetubular fixture 44 and an axis Ja of the insertion hole 26 (operatingrod 11) are coaxial arranged, while an axis Ka of each of thethrough-holes 27 for the four bolts 28 in the partitioning wall portion24 and an axis Kb of each of the screw holes 45 into which the bolts 28are screwed in the mounting base 42 are coaxially arranged (that is,they are aligned (centered)). Thus, any misalignment between the bodycasing 23 and the motor assembly 25 can be fixed.

Therefore, when the four bolts 28 are screwed through the through-holes27 into the screw holes 45 to secure (finally secure) the motor assembly25 to the partitioning wall portion 24 as illustrated in FIG. 12, eachof the through-holes 27 and each of the screw holes 45 are aligned in astraight line. This facilitates the screwing work.

Similarly, the tubular fixture 44 (rotary drive shaft 33 of the motor30) and the insertion hole 26 (operating rod 11 and power transmissionshaft 12) are concentrically arranged, which facilitates couplingbetween the tubular fixture 44 and the operating rod 11 (main operatingrod 11A) and between the rotary drive shaft 33 and the powertransmission shaft 12.

[Functional Effects]

As is obvious from the description above, in the electric workingmachine 1 of the present embodiment, the four components of the motor30, control board 80, rod fixture 40, and air guiding partitioningmember 60 are integrally formed as the motor assembly 25 as a singlearticle. This can simplify and accelerate the assembling work.

Further, the motor assembly 25 can be temporarily secured to the bodycasing 23. In such temporary securing, the body casing 23 and the motorassembly 25 are automatically aligned (centered). Therefore, theoperator is not required to hold the motor assembly 25 or to aligncomponents, as conventionally required. Also, elimination of the needfor specific jigs can simplify the assembling work and effectivelyreduce the man-hours and production cost.

In addition, the motor assembly 25 can be attached to the body casing 23only by screwing the bolts 28 from the outer side of the body casing 23.This also facilitates the assembling work.

When the motor assembly 25 needs to be taken out from the body casing 23for maintenance or components replacement, it is only necessary toremove the bolts 28 and then widen the bracing pieces 29 with fingers orthe like. The bracing pieces 29 may be reused when the removed motorassembly 25 is securely attached again. When the bracing pieces 29 areno longer needed, they can be cut away.

As described above, with the air guiding partitioning member 60 providedin the rear portion of the body casing 23, the cooling air taken in fromthe air intake port 22 moves upward while cooling the cooling fin 85 andcapacitor 82 that are supposed to have a high temperature, flows throughthe air guiding window 64 in the upper portion of the partitioning plate62 and the space 66 between the motor 30 and the body casing 23, issucked into the motor 30 from the opening 36 for sucking air (see FIG.7) on the front side of the motor 30, and is blown out toward the airexhaust port 21 from the air outlet 34 a for exhausting air by thecooling fan, as illustrated in FIG. 19.

In the present embodiment, with the air guiding partitioning member 60partitioning the air exhaust port 21 and the air intake port 22, ahigh-temperature exhaust air is unlikely to mix with a low-temperatureintake air. Further, the control board 80 is disposed on the rear sideof the partitioning plate 62 to allow the cooling air from the airintake port 22 to be easily blown onto the electronic components thatare supposed to have a high temperature. Thus, the control board 80 canbe efficiently cooled and the electronic components (such as thecapacitor 82) mounted on the control board 80 are less likely todeteriorate due to the heat.

With the air exhaust port 21 and the air intake port 22 provided on thebottom 23 b of the body casing 23, another advantageous effect ofreducing dust and rainwater entering the body casing 23 can be obtained.

In the aforementioned embodiment, the portable electric working machineincluding the common machine body and exchangeable working parts(attachments) has been described as an example. However, the electricworking machine is not limited thereto, and may be a common bush cutter,hedge trimmer, chain saw, or the like, having no exchangeable workingparts (that is, the working part is not exchangeable).

What is claimed is:
 1. An electric working machine comprising: a motoras a driving source for operation; a body casing in which the motor isdisposed in a longitudinal direction; an operating rod provided with aworking part; and a rod fixture for securely attaching the operating rodto the body casing, wherein: the motor, a control board for controllingthe motor, the rod fixture secured to a front side of the motor, and anair guiding partitioning member secured to a rear side of the motor forma motor assembly, the air guiding partitioning member includes apartitioning plate that hermetically partitions between an air exhaustport and an air intake port provided with a predetermined interval inthe longitudinal direction in the body casing, the partitioning plateprovided with an air guiding window for delivering cooling air taken infrom the air intake port to an opening for sucking air on the front sideof the motor through a space between the motor and the body casing, andthe control board is disposed on a rear side of the partitioning plate.2. The electric working machine according to claim 1, wherein the airexhaust port and the air intake port are provided on a bottom of thebody casing in the longitudinal direction, and the air guiding window isprovided in an upper portion of the partitioning plate.
 3. The electricworking machine according to claim 2, wherein electronic components thatare supposed to have a high temperature are mounted in a lower portionof the control board, and a guide member with a widened and open lowerportion is provided in the control board to allow more cooling air takenin from the air intake port to flow through the electronic componentsthat are supposed to have a high temperature.
 4. The electric workingmachine according to claim 3, wherein the guide member is integrallyformed with the partitioning plate.
 5. The electric working machineaccording to claim 1, wherein the air guiding partitioning memberincludes a recessed housing that covers at least part of a fan caseprovided in a rear portion of the motor.
 6. The electric working machineaccording to claim 1, wherein: the body casing has a single cylindricalbody with an open front end and an open rear end and with a partitioningwall portion that partitions an inside of the body casing into a frontportion and a rear portion, and the rod fixture includes: a mountingbase disposed behind the partitioning wall portion and is securelyfastened to the partitioning wall portion, with at least one boltscrewed from a front side to a rear side of the partitioning wallportion through a through-hole provided in the partitioning wallportion; and a tubular fixture for securing a proximal end of theoperating rod, the tubular fixture projecting from the mounting basetoward a front of the partitioning wall portion through an insertionhole provided in the partitioning wall portion.